JP2012186413A - Semiconductor light-emitting element and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor light-emitting element with high luminous efficiency.SOLUTION: A semiconductor light-emitting element comprises: an n-type nitride semiconductor layer; an active layer of a nitride semiconductor on the n-type nitride semiconductor layer; and a p-type nitride semiconductor layer on the active layer. The p-type nitride semiconductor layer includes an aluminum gallium nitride layer. The indium concentration in the aluminum gallium nitride layer ranges from 1E18atoms/cmor more to 1E20atoms/cmor less, and the carbon concentration in the aluminum gallium nitride layer is 6E17atoms/cmor less. When the magnesium concentration in the aluminum gallium nitride layer is X and the acceptor concentration in the aluminum gallium nitride layer is Y, the following formula is satisfied: Y>{(-5.35e19)-(X-2.70e19)}-4.63e19.

Description

  Embodiments described herein relate generally to a semiconductor light emitting device and a method for manufacturing the same.

Group III nitride semiconductors are used as materials for semiconductor light emitting devices such as laser diodes (LDs) and light emitting diodes (LEDs). The group III nitride semiconductor is represented by a general formula Al _x Ga _y In _1-xy N (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1).

  In a semiconductor light emitting device using a group III nitride semiconductor, it is required to improve the light emission efficiency of the device. For this reason, the element structure and manufacturing method which improve luminous efficiency are searched.

JP 2003-309074 A

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a semiconductor light emitting device having high luminous efficiency and a method for manufacturing the same.

The semiconductor light emitting device of the embodiment includes an n-type nitride semiconductor layer, a nitride semiconductor active layer on the n-type nitride semiconductor layer, and a p-type nitride semiconductor layer on the active layer. The p-type nitride semiconductor layer includes an aluminum gallium nitride layer, the indium concentration in the aluminum gallium nitride layer is 1E18 atoms / cm ³ or more and 1E20 atoms / cm ³ or less, the carbon concentration is 6E17 atoms / cm ³ or less, and magnesium When the density is X and the acceptor density is Y,
Y> {(− 5.35e19) ² − (X−2.70e19) ² } ^1/2 −4.63e19
It is.

It is sectional drawing of the semiconductor light-emitting device of embodiment. It is a figure explaining the effect | action of the semiconductor light-emitting device of embodiment. It is a figure explaining the effect | action of the semiconductor light-emitting device of embodiment. It is a figure which shows the device characteristic of the semiconductor light-emitting device of embodiment.

  Hereinafter, embodiments will be described with reference to the drawings.

The inventors paid attention to the composition of the aluminum gallium nitride (Al _x Ga _1-x N (0 <x <1)) layer in the p-type nitride semiconductor layer in order to increase the luminous efficiency of the semiconductor light emitting device. Then, indium (In) is contained in the aluminum gallium nitride (Al _x Ga _1-x N (0 <x <1)) layer, the ratio of the acceptor concentration to the magnesium (Mg) concentration is increased, and carbon It has been found that the light emission efficiency of the semiconductor light emitting device can be improved by reducing the concentration.

The aluminum gallium nitride layer having the above composition can be formed by supplying nitrogen (N ₂ ) gas as an indium raw material and a carrier gas in a growth atmosphere by metal organic chemical vapor deposition (MOCVD). I found.

In forming an aluminum gallium nitride layer containing magnesium as a p-type impurity, the inventors first introduced that nitrogen (N ₂ ) gas as a carrier gas is introduced into the growth atmosphere to increase the acceptor concentration. I found it.

  However, by introducing nitrogen gas, especially in film growth at a low temperature of 1000 ° C. or lower, the carbon (C) concentration increases, and light emission caused by deterioration of crystallinity of aluminum gallium nitride and deterioration of hole mobility is achieved. It became clear that a reduction in efficiency occurred. Moreover, the controllability of the acceptor concentration by magnesium is reduced by increasing the carbon concentration.

  In contrast to this, the inventors have added the indium raw material to the atmosphere in addition to the nitrogen gas of the carrier gas, so that the carbon concentration of the aluminum gallium nitride layer is reduced and the ratio of the acceptor concentration to the magnesium concentration is It became clear that the emission efficiency was improved as a result.

  The following embodiments are based on the above findings found by the inventors.

The semiconductor light emitting device of the embodiment includes an n-type nitride semiconductor layer, a nitride semiconductor active layer on the n-type nitride semiconductor layer, and a p-type nitride semiconductor layer on the active layer. The p-type nitride semiconductor layer includes an aluminum gallium nitride layer, the indium (atom) concentration in the aluminum gallium nitride layer is 1E18 atoms / cm ³ or more and 1E20 atoms / cm ³ or less, and the carbon (atom) concentration is 6E17 atoms / cm. ³ or less, when the magnesium (atom) concentration is X (atoms / cm ³ ) and the acceptor concentration is Y (atoms / cm ³ ),
Y> {(− 5.35e19) ² − (X−2.70e19) ² } ^1/2 −4.63e19
It is.

  According to the semiconductor light emitting device of the present embodiment, high emission efficiency is realized because the ratio of the acceptor concentration to the magnesium concentration which is the p-type impurity in the aluminum gallium nitride layer is high and the carbon concentration is low.

  Hereinafter, a ridge stripe type laser diode (LD) will be described as an example of the semiconductor light emitting device.

  FIG. 1 is a cross-sectional view of the semiconductor light emitting device of this embodiment. 1A is a cross-sectional view parallel to the extending direction of the ridge stripe, and FIG. 1B is a cross-sectional view taken along line AA of FIG. 1A.

The semiconductor laser diode which is the semiconductor light emitting device of the present embodiment is formed using a group III nitride semiconductor. As a GaN-based n-type nitride semiconductor layer 12 on an n-type GaN (gallium nitride) semiconductor substrate 10, for example, Si-doped n-type Al _0.05 Ga _0.95 N with a thickness of 1200 nm is used. An n-type cladding layer 12a and a 100-nm thick Si-doped n-type GaN n-type guide layer 12b are formed.

On the n-type nitride semiconductor layer 12, a GaN-based semiconductor having a multiple quantum well structure (MQW), for example, In _0.12 Ga _0.88 N with a thickness of 3 nm / In _0.03 Ga _{0 with a} thickness of 10 nm. The active layer 14 having a multiple structure of ₉₇ N is formed.

On the active layer 14, as the GaN-based p-type nitride semiconductor layer 16, for example, a 100-nm-thick Mg-doped p-type GaN p-type guide layer 16a and a 600-nm-thick Mg-doped p-type An Al _0.05 Ga _0.95 N p-type cladding layer 16b and a 10-nm-thick Mg-doped p-type GaN p-type contact layer 16c are formed.

Although not shown, for example, a 10-nm-thick Mg-doped p-type Al _0.2 Ga _0.8 N overflow prevention layer may be formed between the p-type guide layer 16a and the p-type cladding layer 16b. It doesn't matter. The p-type guide layer 16a may be undoped.

  The p-type nitride semiconductor layer 16 is provided with a ridge stripe 18 for forming a laser light waveguide region. The side surfaces of the ridge stripe 18 and the surface of the p-type cladding layer 16b are covered with, for example, an insulating film 20 of a silicon oxide film.

  An n-side electrode 24 is provided on the lower surface of the substrate 10, and a p-side electrode 26 is provided on the p-type contact layer 16c.

The Mg-doped p-type Al _0.05 Ga _0.95 N p-type cladding layer 16b contains 1E18 atoms / cm ³ or more and 1E20 atoms / cm ³ or less of indium. Thus, by containing indium, indium functions as a surfactant and improves crystallinity. Below the above range, a sufficient surfactant cannot be obtained. On the other hand, if the above range is exceeded, a quaternary mixed crystal is formed, and there is a possibility that the device characteristics will change greatly. In this respect, the concentration of indium is more preferably at most 3E18atoms / cm ³ or more 3E19atoms / cm ^3, it is even more preferably not more than 8E18atoms / cm ³ or more 3E19atoms / cm ^3.

In the p-type cladding layer 16b, when the magnesium (atom) concentration is X (atoms / cm ³ ) and the acceptor concentration is Y (atoms / cm ³ ),
Y> {(− 5.35e19) ² − (X−2.70e19) ² } ^1/2 −4.63e19
It is. The magnesium concentration is 1E18 atoms / cm ³ or more and 1E20 atoms / cm ³ or less, more preferably 5E18 atoms / cm ³ or more and 5E19 atoms / cm ³ or less, and further preferably 1E19 atoms / cm ³ or more and 3E19 atoms / cm ³ or less.

  When the magnesium concentration is below the above range, the ratio of the acceptor concentration to the magnesium concentration is low, and there is a possibility that sufficient conductivity is not ensured in the p-type nitride semiconductor layer. In addition, when exceeding the above range, the acceptor concentration of magnesium is lowered, and there is a possibility that sufficient conductivity is not ensured in the p-type nitride semiconductor layer.

The p-type cladding layer 16b has a carbon concentration of 6E17 atoms / cm ³ or less. Thus, by suppressing the carbon concentration, the mobility of holes is improved, and the conductivity of the p-type nitride semiconductor layer is improved. Therefore, improvement in luminous efficiency can be expected. In addition, by suppressing the carbon concentration, the controllability of the acceptor concentration by adding magnesium is improved, the characteristics of the semiconductor light emitting device are stabilized, and an improvement in manufacturing yield can be expected. The carbon concentration is more preferably 1E17 atoms / cm ³ or less.

  Note that the concentrations of indium, magnesium, and carbon can be evaluated by a SIMS (Secondary Ion Mass Spectrometry) method. Further, the acceptor concentration can be evaluated by an ECV (Electro Chemical Voltammetry) method.

  Next, a method for manufacturing the semiconductor light emitting device of this embodiment will be described with reference to FIG.

On the n-type GaN substrate 10, an Al _0.05 Ga _0.95 N n-type cladding layer 12 a, a GaN n-type guide layer 12 b, and In _0.12 Ga _{0 are formed} by metal organic chemical vapor deposition (MOCVD). _.88 N / In _0.03 Ga _0.97 N multi-layer active layer 14, GaN p-type guide layer 16a, Al _0.05 Ga _0.95 N p-type cladding layer 16b, GaN p-type contact Layer 16c is formed sequentially.

Next, a SiO ₂ film is deposited on the upper surface of the p-type contact layer 16c. A mask having a width of about 10 μm is formed to form a ridge stripe by patterning using a resist and etching using ammonium fluoride. Etching is performed halfway through the p-type clad layer 16b of Al _0.05 Ga _0.95 N using a mask by a dry etching apparatus to form a ridge stripe 18.

After removing the mask, the insulating film 20 is formed on the side surfaces of the ridge stripe 18 and the surface of the p-type cladding layer 16b by depositing a SiO ₂ film and patterning using a resist, for example.

  Thereafter, an electrode metal for the p-side electrode is deposited and patterned to form the p-side electrode 26. Further, after polishing the GaN substrate 10 on the side opposite to the ridge stripe 18 to form a thin film, an electrode metal for an n-side electrode is deposited and patterned to form an n-side electrode 24.

  Then, a scribe line is formed on the surface of the n-type GaN substrate 10 along the cleavage direction perpendicular to the ridge stripe. Starting from this scribe line, the n-type GaN substrate 10 is separated in a bar shape along the cleavage plane.

  Further, the n-type GaN substrate in the shape of a bar is scribed and braked in the short direction to manufacture one semiconductor light emitting device as shown in FIG.

  In the present embodiment, during the growth of the aluminum gallium nitride p-type cladding layer 16b by the MOCVD method, a nitrogen gas is supplied as a magnesium source, an indium source, and a carrier gas in a growth atmosphere. That is, during the growth of the p-type cladding layer 16b, an aluminum source, a gallium source, a magnesium source, an indium source, and a nitrogen source are supplied into the growth atmosphere. Nitrogen gas is supplied as a carrier gas for these raw materials.

Examples of the aluminum raw material include trimethylaluminum (TMA) and triethylaluminum (TEA). The gallium raw material is, for example, trimethyl gallium (TMG) or triethyl gallium (TEG). The magnesium raw material is, for example, cyclopentadienyl magnesium (Cp ₂ Mg). The nitrogen raw material is, for example, ammonia (NH ₃ ).

  The indium raw material is, for example, trimethylindium (TMI) or triethylindium (TEI). The supply amount of the indium raw material supplied into the growth atmosphere during the growth of aluminum gallium nitride is desirably 50% or more, and larger than 100%, relative to the sum of the supply amounts of the aluminum raw material and the gallium raw material. Is more desirable. Depending on the component of the carrier gas, such as when hydrogen is contained in the carrier gas, it is difficult to obtain a sufficient In concentration below the above range, and therefore a sufficient carbon reduction effect cannot be obtained.

  Here, the supply amount of the raw material is the supply amount of the raw material represented by the number of atoms represented by the number of atoms per unit time. For example, it is expressed in mol / min.

The nitrogen gas is not necessarily 100% nitrogen, and may be a mixed gas of nitrogen gas and hydrogen (H ₂ ) gas or other gas. However, the flow rate of the nitrogen gas is preferably 10% or more of the total flow rate of the carrier gas, more preferably 50% or more, further preferably 90% or more, and preferably 99% or more. More desirable. This is because the ratio of the acceptor concentration to the magnesium concentration increases as the flow rate of nitrogen gas increases.

  The growth temperature of aluminum gallium nitride is preferably 700 ° C. or higher and 1100 ° C. or lower, more preferably 800 ° C. or higher and 1000 ° C. or lower. Below the above range, the crystallinity of aluminum gallium nitride may be deteriorated. On the other hand, if it exceeds the above range, the characteristics of the light-emitting element may be deteriorated by applying thermal stress during growth to a lower semiconductor layer such as an active layer.

  FIG. 2 is a diagram for explaining the operation of the semiconductor light emitting device of the embodiment. Growth conditions for forming a single layer film of aluminum gallium nitride by MOCVD were changed. The relationship between the indium concentration of the formed aluminum gallium nitride and the carbon concentration is shown. Each growth condition is as follows.

(Condition 1): Diamond mark in FIG. 2. Growth temperature: 1030 ° C.
Raw materials: TMA, TMG, Cp ₂ Mg, NH ₃
-TMI supply amount / (TMA supply amount + TMG supply amount) = 0%
-Carrier gas: nitrogen gas, hydrogen gas-Nitrogen gas flow rate / carrier gas total flow rate = 48.8%

(Condition 2): In FIG. 2, white circle (○) mark • Growth temperature: 1000 ° C
Raw materials: TMA, TMG, Cp ₂ Mg, NH ₃
-TMI supply amount / (TMA supply amount + TMG supply amount) = 0%
-Carrier gas: nitrogen gas, hydrogen gas-Nitrogen gas flow rate / carrier gas total flow rate = 98.6%

(Condition 3): In FIG. 2, white triangle (△) mark ・ Growth temperature: 1000 ° C.
Raw materials: TMA, TMG, TMI 4.6 μmol / min, Cp ₂ Mg, NH ₃
TMI supply amount / (TMA supply amount + TMG supply amount) = 5.9%
-Carrier gas: nitrogen gas, hydrogen gas-Nitrogen gas flow rate / carrier gas total flow rate = 98.6%

(Condition 4): In FIG. 2, white square (□) mark ・ Growth temperature: 1000 ° C.
Raw materials: TMA, TMG, TMI 15.8 μmol / min, Cp ₂ Mg, NH ₃
-TMI supply amount / (TMA supply amount + TMG supply amount) = 19.8%
-Carrier gas: nitrogen gas, hydrogen gas-Nitrogen gas flow rate / carrier gas total flow rate = 98.6%

(Condition 5): Black circle (●) in FIG. 2 ・ Growth temperature: 940 ° C.
Raw materials: TMA, TMG, Cp ₂ Mg, NH ₃
-TMI supply amount / (TMA supply amount + TMG supply amount) = 0%
-Carrier gas: nitrogen gas, hydrogen gas-Nitrogen gas flow rate / carrier gas total flow rate = 48.8%

(Condition 6): Black square (■) mark in FIG. 2 Growth temperature: 940 ° C.
Raw materials: TMA, TMG, TMI 47.2 μmol / min, Cp ₂ Mg, NH ₃
-TMI supply amount / (TMA supply amount + TMG supply amount) = 59.1%
-Carrier gas: nitrogen gas, hydrogen gas-Nitrogen gas flow rate / carrier gas total flow rate = 48.8%

  As described above, when nitrogen gas is used as the carrier gas, the acceptor concentration in aluminum gallium nitride increases, but the carbon concentration also increases. This tendency becomes prominent when the nitrogen gas flow rate / carrier gas total flow rate increases. In addition, it becomes prominent when the growth temperature is lowered. This tendency can also be read by comparing condition 1 (diamond mark), condition 2 (◯ mark), and condition 5 (● mark) where TMI is not supplied in FIG.

  However, by supplying the indium raw material as shown in FIG. 2, the carbon concentration in the aluminum gallium nitride can be reduced even if nitrogen gas is used as the carrier gas.

  FIG. 3 is a diagram for explaining the operation of the semiconductor light emitting device of the embodiment. The relationship between the atomic concentration of magnesium and the acceptor concentration in aluminum gallium nitride formed under conditions 2 (◯ mark), condition 3 (Δ mark), and condition 4 (□ mark) is shown. The concentration is measured by SIMS, and the acceptor concentration is measured by ECV.

As shown in FIG. 3, as the TMI flow rate increases, the acceptor concentration increases even at the same atomic concentration of magnesium. That is, the activation rate of magnesium is improved. And, by introducing the indium raw material, when the magnesium concentration is X and the acceptor concentration is Y,
Y> {(− 5.35e19) ² − (X−2.70e19) ² } ^1/2 −4.63e19
Is established.

  FIG. 4 is a diagram illustrating device characteristics of the semiconductor light emitting device of the embodiment. In the laser diode having the structure of FIG. 1, the TMI is supplied as the growth condition of the p-type cladding layer 16b of aluminum gallium nitride and the above condition 2 (circle in FIG. 2, FIG. 3, circled in FIG. 4) is supplied. Conditions 4 (marked in FIG. 2 and FIG. 3; solid line in FIG. 4) were applied to evaluate the device characteristics.

  As can be seen from FIG. 4, by supplying the indium raw material, the operating voltage is reduced and the luminous efficiency is improved. This is because when nitrogen gas is used as a carrier gas and an indium raw material is supplied, the activation rate of magnesium is improved and the mobility of holes is also improved by reducing the carbon concentration, and the conductivity of the p-type cladding layer 16b is improved. This is thought to be due to the improvement.

  According to the manufacturing method of the embodiment, the acceptor concentration of magnesium in the p-type aluminum gallium nitride is improved and the carbon concentration is reduced. Therefore, the conductivity of the p-type nitride semiconductor layer is improved, and it becomes possible to provide a semiconductor light emitting device with high luminous efficiency.

  And according to the manufacturing method of embodiment, an effect arises also at the low temperature of 1000 degrees C or less or 950 degrees C or less. Accordingly, thermal stress on the underlayer during the growth of aluminum gallium nitride is also suppressed. Also from this point of view, it is possible to provide a semiconductor light emitting device with high luminous efficiency and excellent characteristics.

  The embodiments of the present invention have been described above with reference to specific examples. The above embodiment is merely given as an example, and does not limit the present invention. Further, the constituent elements of the respective embodiments may be appropriately combined.

  In the description of the embodiments, the description of the semiconductor light emitting device and the manufacturing method thereof, etc., which is not directly necessary for the description of the present invention is omitted, but the required semiconductor light emitting device and the manufacturing method thereof are described. The elements related to can be appropriately selected and used.

  For example, in the embodiment, a laser diode (LD) is described as an example of a semiconductor light emitting element, but the present invention can also be applied to a light emitting diode (LED).

  In addition, the present invention can be applied to any layer as long as it is a p-type aluminum gallium nitride layer used in a semiconductor light emitting device, not limited to a p-type cladding layer of an LD.

  In addition, all semiconductor light-emitting elements that include the elements of the present invention and that can be appropriately modified by those skilled in the art and methods for manufacturing the same are included in the scope of the present invention. The scope of the present invention is defined by the appended claims and equivalents thereof.

10 substrate 12 n-type nitride semiconductor layer 14 active layer 16 p-type nitride semiconductor layer 16b p-type cladding layer (aluminum gallium nitride layer)

Claims (5)

an n-type nitride semiconductor layer;
An active layer of nitride semiconductor on the n-type nitride semiconductor layer;
A p-type nitride semiconductor layer on the active layer,
The p-type nitride semiconductor layer includes an aluminum gallium nitride layer, the indium concentration in the aluminum gallium nitride layer is 1E18 atoms / cm ³ or more and 1E20 atoms / cm ³ or less, the carbon concentration is 6E17 atoms / cm ³ or less, and magnesium When the density is X and the acceptor density is Y,
Y> {(− 5.35e19) ² − (X−2.70e19) ² } ^1/2 −4.63e19
A semiconductor light emitting element characterized by the above. The indium concentration is 3E18 atoms / cm ³ or more and 3E19 atoms / cm ³ or less, the carbon concentration is 6E17 atoms / cm ³ or less, and the magnesium concentration is 5E18 atoms / cm ³ or more and 5E19 atoms / cm ³ or less. Semiconductor light emitting device. An n-type nitride semiconductor layer, an active layer of nitride semiconductor, and a p-type nitride semiconductor layer including an aluminum gallium nitride layer containing magnesium are sequentially formed on the substrate by metal organic chemical vapor deposition (MOCVD). A method for manufacturing a semiconductor light emitting device, comprising:
During the growth of the aluminum gallium nitride layer, a magnesium source material, an indium source material, and a nitrogen gas as a carrier gas are supplied in a growth atmosphere.   4. The method of manufacturing a semiconductor light emitting device according to claim 3, wherein the growth temperature of the aluminum gallium nitride layer is 700 ° C. or higher and 1100 ° C. or lower.   5. The method of manufacturing a semiconductor light emitting device according to claim 3, wherein the flow rate of the nitrogen gas is 10% or more of the total flow rate of the carrier gas.

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